Conventionally, to detect the positions of substrates such as semiconductor substrates (hereinafter referred to as “wafers”) during a manufacturing process, semiconductor manufacturing apparatus are provided with a wafer state detecting mechanism. Such a wafer state detecting mechanism judges whether or not wafer states in a manufacturing process are normal by comparing, for example, intervals between adjoining wafers or the positions of wafers in other slots that are placed in a boat with preset position information. That is, in the conventional wafer state detecting method, intervals (hereinafter referred to as “wafer pitches”) between adjoining wafers placed in a boat are compared with preset position information and a judgment result “normal states” is produced if positional deviations (interval deviations) are smaller than or equal to an allowable error limit Δt for successful transport by a wafer transfer machine.
In the field of semiconductor manufacturing apparatus, many techniques for performing prescribed semiconductor manufacturing processing while detecting wafer positions have been reported. For example, a technique is disclosed in which wafer position data are acquired in advance for the three lowest stages of a boat, whether or not boat groove positions are within an allowable range is judged, placement positions are registered, and transport is performed (refer to Patent document 1, for example). Another technique is disclosed in which in detecting the positions of wafers in a boat, the origin position of the boat is employed as a detection start position (refer to Patent document 2, for example). A further technique is disclosed in which the inclination of a boat is detected by checking the position of a boat main body with a position sensor (refer to Patent document 3, for example).
Patent document 1: JP-A-7-142553
Patent document 2: JP-A-5-41442
Patent document 3: JP-A-6-298315